There have been developed inhalation apparatuses which make and eject minute droplets of a drug using the ejection principle of an ink jet system, and make a user inhale them in an air flow path through which air inhaled through a mouthpiece flows (refer to Japanese Patent Application Laid-Open Nos. 2004-290593 and 2004-283245). Such inhalation apparatuses have an advantage of being able to spray a predetermined amount of drug precisely in an equalized particle diameter.
As the fundamental construction of such a drug ejecting apparatus, there are an ejection head in which an ejection energy generating element, such as a heat-generating element, is arranged, and a drug tank which contains the drug supplied to the ejection head. Here, in order to absorb efficiently medical fluid, which is ejected, in the lungs, it is important that the droplet diameter is extremely minute, as small as several microns, and, as for an orifice diameter of the ejection head, a dimension of several microns is therefore required.
In addition, in the field of ink jet recording apparatuses, a method of securing negative pressure in an ink tank by sucking an outside space of a flexible ink tank indirectly with a pump for negative pressure generation is known (refer to Japanese Patent Application Laid-Open No. H06-079881).
An ejection head, prior to be used for the first time, is not filled with the drug in a drug tank to the ejection port. In addition, also at the time of second or later use, a restoring operation of replacing the drug near the ejection port, to perform what is termed “refreshing”, may be needed. In this point, it is common to perform suction with a vacuum pump from the outside of an orifice face of an ejection port in the field of ink jet recording apparatuses, and to perform a first-time filling operation and second-time and later restoring operations.
On the other hand, in the ink jet system, in order to perform proper ejection once an ejection head is filled with a drug, proper negative pressure must be secured inside the ejection head orifice. It turns out that, when an ejection port performs ejection with 3 μm of ejection head, it can be performed to maintain pressure inside an ejection head orifice in the range of −1 kPa to −5 kPa based on outside pressure. The pressure inside the orifice is almost equivalent to the inside pressure of the drug tank connected to the ejection head here.
The apparatus will be made larger by the inclusion of a suction pump, when filling and restoring operations are intended to perform with a suction pump, as is conventional, or where it is intended to secure negative pressure in a drug tank by the method described in Japanese Patent Application Laid-Open No. H06-079881. This is not suitable in a drug ejecting apparatus for which portability is required, such as an inhalation apparatus.